Leak checking method, leak checking apparatus, electroplating method, and electroplating apparatus

ABSTRACT

There is disclosed an improved leak checking method which can accurately test a sealing performance of a substrate holder more than conventional leak check techniques. The leak checking method includes: holding a substrate with a substrate holder, the substrate holder including a first holding member and a second holding member, the second holding member having an opening through which a surface of the substrate is exposed; pressing a sealing projection of the second holding member against the surface of the substrate when holding the substrate with the substrate holder; covering the surface of the substrate, exposed through the opening, and the sealing projection with a sealing cap; forming a hermetic space between the sealing cap and the substrate holder; introducing a pressurized gas into the hermetic space; and detecting a decrease in pressure of the pressurized gas in the hermetic space.

CROSS REFERENCE TO RELATED APPLICATION

This document claims priority to Japanese Patent Application No.2016-221906 filed Nov. 14, 2016, the entire contents of which are herebyincorporated by reference.

BACKGROUND

An electroplating apparatus for plating a substrate, such as a wafer,uses a substrate holder for detachably holding the substrate. Thesubstrate held by the substrate holder is immersed in a platingsolution. When a voltage is applied between an anode and the substrate,electric current flows from the anode to the substrate through theplating solution, whereby a surface of the substrate is plated in thepresence of the plating solution.

The substrate holder for use in electroplating has an electrical contactwhich contacts the to-be-plated surface of the substrate. The substrateholder has a sealing function to prevent intrusion of the platingsolution so that during plating of the substrate, the plating solutiondoes not come into contact with the electrical contact of the substrateholder which is immersed in the plating solution. When the substrateholder holds the substrate, a hermetic space is formed in the interiorof the substrate holder, and the electrical contact is located in thishermetic space.

If the sealing performance of the substrate holder is lowered, theplating solution may intrude into the hermetic space in the substrateholder and come into contact with the electrical contact. There areseveral techniques for testing a sealing performance of such a substrateholder, as disclosed in Japanese Laid-open Patent Publication No.2003-277995 and Japan Patent No. 5782398.

SUMMARY OF THE INVENTION

According an embodiment, there is provided an improved leak checkingapparatus and an improved leak checking method which can accurately testa sealing performance of a substrate holder more than conventional leakcheck techniques.

According an embodiment, there is provided an electroplating apparatusand an electroplating method including such a leak checking apparatusand such a leak checking method, respectively.

Embodiments, which will be described below, relate to a leak checkingmethod and a leak checking apparatus for testing a sealing performanceof a substrate holder for holding a substrate, such as a wafer. Thebelow-described embodiments also relate to an electroplating method andan electroplating apparatus including such a leak checking method andsuch a leak checking apparatus, respectively.

In an embodiment, there is provided a leak checking method comprising:holding a substrate with a substrate holder, the substrate holderincluding a first holding member and a second holding member, the secondholding member having an opening through which a surface of thesubstrate is exposed; pressing a sealing projection of the secondholding member against the surface of the substrate when holding thesubstrate with the substrate holder; covering the surface of thesubstrate, exposed through the opening, and the sealing projection witha sealing cap; forming a hermetic space between the sealing cap and thesubstrate holder; introducing a pressurized gas into the hermetic space;and detecting a decrease in pressure of the pressurized gas in thehermetic space.

In an embodiment, the leak checking method further comprises: selectinga pressure command value from a preset pressure range; sending theselected pressure command value to a pressure regulator; and regulatingthe pressure of the pressurized gas in the hermetic space with thepressure regulator based on the pressure command value.

In an embodiment, the pressure range includes a pressure of a platingsolution which is expected to be applied to the sealing projection whenthe substrate, held by the substrate holder, is immersed in the platingsolution.

In an embodiment, a lower limit of the pressure range is a value of apressure of the plating solution which is expected to be applied to anuppermost portion of the sealing projection when the substrate, held bythe substrate holder in a vertical position, is immersed in the platingsolution.

In an embodiment, an upper limit of the pressure range is a valueobtained by multiplying a factor by a value of a pressure of the platingsolution which is expected to be applied to a lowermost portion of thesealing projection when the substrate, held by the substrate holder in avertical position, is immersed in the plating solution.

In an embodiment, forming the hermetic space between the sealing cap andthe substrate holder comprises pressing the sealing cap against thesubstrate holder to form a hermetic space between the sealing cap andthe substrate holder.

In an embodiment, the leak checking method further comprises: pressing apartition seal of the sealing cap against the substrate holder to dividethe hermetic space into a first hermetic space and a second hermeticspace, wherein introducing the pressurized gas into the hermetic spacecomprises supplying the pressurized gas into either the first hermeticspace or the second hermetic space, wherein the sealing projectioncomprises a first sealing projection, and the second holding memberfurther includes a second sealing projection which contacts the firstholding member, and wherein the first sealing projection and the secondsealing projection face the first hermetic space and the second hermeticspace, respectively.

In an embodiment, there is provided a leak checking method comprising:holding a substrate with a substrate holder, the substrate holderincluding a first holding member and a second holding member, the firstholding member having a first opening and a back-side sealingprojection, the second holding member having a second opening and afront-side sealing projection; pressing the front-side sealingprojection and the back-side sealing projection against a front surfaceand a back surface, respectively, of the substrate when holding thesubstrate with the substrate holder; covering the front surface of thesubstrate, exposed through the second opening, and the front-sidesealing projection with a front-side sealing cap; forming a front-sidehermetic space between the front-side sealing cap and the substrateholder; covering the back surface of the substrate, exposed through thefirst opening, and the back-side sealing projection with a back-sidesealing cap; forming a back-side hermetic space between the back-sidesealing cap and the substrate holder; introducing a pressurized gas intothe front-side hermetic space and/or the back-side hermetic space; anddetecting a decrease in pressure of the pressurized gas in thefront-side hermetic space and/or the back-side hermetic space.

In an embodiment, the leak checking method further comprises: selectinga pressure command value from a preset pressure range; sending theselected pressure command value to a pressure regulator; and regulatingthe pressure of the pressurized gas in the front-side hermetic spaceand/or the back-side hermetic space with the pressure regulator based onthe pressure command value.

In an embodiment, the pressure range includes a pressure of a platingsolution which is expected to be applied to the front-side sealingprojection and the back-side sealing projection when the substrate, heldby the substrate holder, is immersed in the plating solution.

In an embodiment, a lower limit of the pressure range is a value of apressure of the plating solution which is expected to be applied to anuppermost portion of the front-side sealing projection or an uppermostportion of the back-side sealing projection when the substrate, held bythe substrate holder in a vertical position, is immersed in the platingsolution.

In an embodiment, an upper limit of the pressure range is a valueobtained by multiplying a factor by a value of a pressure of the platingsolution which is expected to be applied to a lowermost portion of thefront-side sealing projection or a lowermost portion of the back-sidesealing projection when the substrate, held by the substrate holder in avertical position, is immersed in the plating solution.

In an embodiment, there is provided an electroplating method comprising:setting a substrate, to be plated, on a substrate holder in a substrateattachment and detachment section; performing the above-described leakchecking method; immersing the substrate, held by the substrate holder,in a plating solution; and plating the substrate.

In an embodiment, the leak checking method is performed in the substrateattachment and detachment section.

In an embodiment, there is provided a leak checking apparatus forchecking for leakage of a fluid through a sealing projection of asubstrate holder when the sealing projection is being pressed against asurface of a substrate held by the substrate holder which includes afirst holding member and a second holding member, the second holdingmember having the sealing projection and an opening through which asurface of the substrate is to be exposed, said apparatus comprising: asealing cap having a shape that covers the opening and the sealingprojection; a pressurized-gas supply system configured to introduce apressurized gas into a hermetic space formed between the sealing cap andthe substrate holder; and a pressure decrease detector configured todetect a decrease in pressure of the pressurized gas in the hermeticspace.

In an embodiment, the leak checking apparatus further comprises: apressure regulator configured to regulate the pressure of thepressurized gas based on a pressure command value; and an operationcontroller that stores a preset pressure range therein, wherein theoperation controller is configured to send the pressure command value,which has been selected from the pressure range, to the pressureregulator.

In an embodiment, there is provided an electroplating apparatuscomprising: a substrate attachment and detachment section configured toset a substrate, to be plated, on a substrate holder; a plating tankconfigured to hold a plating solution therein; and the above-describedleak checking apparatus.

In an embodiment, the leak checking apparatus is incorporated in thesubstrate attachment and detachment section.

In an embodiment, there is provided a leak checking apparatus forchecking for leakage of a fluid through a front-side sealing projectionand a back-side sealing projection of a substrate holder when thefront-side sealing projection and the back-side sealing projection arebeing pressed against a front surface and a back surface, respectively,of a substrate held by the substrate holder which includes a firstholding member and a second holding member, the first holding memberhaving a first opening and the back-side sealing projection, the secondholding member having a second opening and the front-side sealingprojection, said apparatus comprising: a front-side sealing cap having ashape that covers the second opening and the front-side sealingprojection; a back-side sealing cap having a shape that covers the firstopening and the back-side sealing projection; a pressurized-gas supplysystem configured to introduce a pressurized gas into a front-sidehermetic space formed between the front-side sealing cap and thesubstrate holder, and into a back-side hermetic space formed between theback-side sealing cap and the substrate holder; and a pressure decreasedetector configured to detect a decrease in pressure of the pressurizedgas in the front-side hermetic space and the back-side hermetic space.

In an embodiment, the leak checking apparatus further comprises: apressure regulator configured to regulate the pressure of thepressurized gas based on a pressure command value; and an operationcontroller that stores a preset pressure range, wherein the operationcontroller is configured to send the pressure command value, which hasbeen selected from the pressure range, to the pressure regulator.

In an embodiment, there is provided an electroplating apparatuscomprising: a substrate attachment and detachment section configured toset a substrate, to be plated, on a substrate holder; a plating tankconfigured to hold a plating solution therein; and the above-describedleak checking apparatus.

In an embodiment, the leak checking apparatus is incorporated in thesubstrate attachment and detachment section.

The leak check is performed in the presence of the pressurized gas inthe hermetic space. During the leak check, the pressure of thepressurized gas is applied to a substrate such that the substrate ispressed in a direction away from the sealing projection. Also duringplating of the substrate, the pressure of the plating solution isapplied to the substrate such that the substrate is pressed in adirection away from the sealing projection. Thus, the leak check usingthe pressurized gas is performed under conditions similar to conditionsunder which the substrate is immersed in the plating solution.Therefore, the leak check according to the above-described embodimentscan check the sealing performance of the substrate holder moreaccurately than the conventional leak check using a vacuum pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional front view showing an embodiment ofa plating tank provided in an electroplating apparatus;

FIG. 2 is a schematic cross-sectional view showing a substrate holder;

FIG. 3 is a schematic view showing an embodiment of a leak checkingapparatus for testing sealing performances of a first sealing projectionand a second sealing projection of the substrate holder;

FIG. 4 is a flow chart illustrating a leak checking method performed byusing the leak checking apparatus shown in FIG. 3;

FIG. 5 is a schematic view showing another embodiment of a leak checkingapparatus:

FIG. 6 is a part of a flow chart illustrating a leak checking methodperformed by using the leak checking apparatus shown in FIG. 5:

FIG. 7 is other part of the flow chart, following the part shown in FIG.6:

FIG. 8 is a cross-sectional view showing another embodiment of asubstrate holder;

FIG. 9 is a diagram showing a manner in which the sealing performancesof the first sealing projection and the second sealing projection aretested by using the leak checking apparatus shown in FIG. 3;

FIG. 10 is a diagram showing a manner in which the sealing performanceof a back-side sealing projection is tested by using the leak checkingapparatus shown in FIG. 3;

FIG. 11 is a flow chart of the leak check for the first sealingprojection, the second sealing projection and the back-side sealingprojection of the substrate holder, shown in FIGS. 9 and 10;

FIG. 12 is a diagram showing a manner in which the sealing performancesof the first sealing projection and the second sealing projection aretested by using the leak checking apparatus shown in FIG. 5:

FIG. 13 is a diagram showing a manner in which the sealing performanceof the back-side sealing projection is tested by using the leak checkingapparatus shown in FIG. 5;

FIG. 14 is a flow chart showing the leak check for the first sealingprojection, the second sealing projection and the back-side sealingprojection of the substrate holder, shown in FIGS. 12 and 13;

FIG. 15 is a cross-sectional view showing yet another embodiment of asubstrate holder;

FIG. 16 is a diagram showing an embodiment of a leak checking apparatusfor performing a leak check on the front-side sealing projection and theback-side sealing projection of the substrate holder shown in FIG. 15;

FIG. 17 is a flow chart illustrating an embodiment of a leak checkingmethod performed by using the leak checking apparatus shown in FIG. 16;

FIG. 18 is a part of a flow chart illustrating an embodiment of a leakchecking method performed by using the leak checking apparatus shown inFIG. 16:

FIG. 19 is other part of the flow chart, following the part shown inFIG. 18:

FIG. 20 is a part of a flow chart illustrating an embodiment of a leakchecking method performed by using the leak checking apparatus shown inFIG. 16;

FIG. 21 is other part of the flow chart, following the part shown inFIG. 20; and

FIG. 22 is an overall layout plan view of an embodiment of anelectroplating apparatus.

DESCRIPTION OF EMBODIMENTS

Embodiments will now be described with reference to the drawings.

FIG. 1 is a vertical cross-sectional front view of an embodiment of aplating tank provided in an electroplating apparatus. As shown in FIG.1, a plating solution is held in the plating tank 10. An overflow tank12 for receiving the plating solution that has overflowed a top edge ofthe plating tank 10 is provided adjacent to the plating tank 10.

One end of a plating-solution circulation line 16, which is providedwith a pump 14, is coupled to a bottom of the overflow tank 12, whileother end of the plating-solution circulation line 16 is coupled to abottom of the plating tank 10. The plating solution that has accumulatedin the overflow tank 12 is returned through the plating-solutioncirculation line 16 to the plating tank 10 by the actuation of the pump14. A temperature control unit 20 for controlling the temperature of theplating solution, and a filter 22 for removing foreign matter from theplating solution, both located downstream of the pump 14, are attachedto the plating-solution circulation line 16.

The electroplating apparatus includes a substrate holder 24 fordetachably holding a substrate (which is an object to be plated) W, suchas a wafer, and immersing the substrate W in a vertical state in theplating solution held in the plating tank 10. The electroplatingapparatus further includes an anode 26 disposed in the plating tank 10,and an anode holder 28 holding the anode 26. When the substrate holder24, holding the substrate W, is set in the plating tank 10, thesubstrate W and the anode 26 face each other in the plating tank 10. Thesubstrate W has a surface conductive layer (e.g. a seed layer) formedtherein in advance. The anode 26 is electrically connected to a positivepole of a power source 30, and the conductive layer of the substrate Wis connected via the substrate holder 24 to a negative pole of the powersource 30. When the power source 30 applies a voltage between the anode26 and the substrate W, plating of the substrate W progresses in thepresence of the plating solution, thus depositing a metal (e.g. copper)on the surface of the substrate W.

A paddle 32, which is configured to reciprocate parallel to the surfaceof the substrate W to agitate the plating solution, is disposed betweenthe substrate holder 24 and the anode 26. By agitating the platingsolution with the paddle 32, a sufficient amount of metal ions can besupplied uniformly to the surface of the substrate W. A regulation plate34 made of a dielectric material is disposed between the paddle 32 andthe anode 26 for making distribution of electric potential more uniformover the entire surface of the substrate W.

FIG. 2 is a schematic cross-sectional view showing the substrate holder24. The substrate holder 24 is adapted to be used in the electroplatingapparatus for electroplating the substrate W such as a wafer. As shownin FIG. 2, the substrate holder 24 includes a first holding member 38and a second holding member 40 for holding the substrate W. The secondholding member 40 is secured to the first holding member 38 by acoupling mechanism 41.

The coupling mechanism 41 includes a first coupling member 42 secured tothe first holding member 38, and a second coupling member 43 secured tothe second holding member 40. The second coupling member 43 is mountedto an outer surface of the second holding member 40. The first couplingmember 42 and the second coupling member 43 are configured to beengageable with each other. When the first coupling member 42 and thesecond coupling member 43 are engaged with each other, the secondholding member 40 is secured to the first holding member 38. The secondholding member 40 can be detached from the first holding member 38 bydisengaging the first coupling member 42 and the second coupling member43.

The first holding member 38 has a substrate support surface 38 a forsupporting a back surface of the substrate W. The substrate W is placedon the substrate support surface 38 a. The second holding member 40 hasan opening 40 a which is smaller than a front surface of the substrateW. In this embodiment, the opening 40 a has a circular shape, and itsdiameter is smaller than the diameter of the substrate W. When thesubstrate W is held by the substrate holder 24, the front surface of thesubstrate W is exposed through the opening 40 a. The front surface ofthe substrate W is a surface to be plated.

The second holding member 40 has a first sealing projection 48 and asecond sealing projection 47, each having an endless shape. The firstsealing projection 48 and the second sealing projection 47 may each be asealing member such as an O-ring. In an embodiment, the second holdingmember 40 itself, including the first sealing projection 48 and thesecond sealing projection 47, may be formed of a material having asealing function. In this embodiment, the first sealing projection 48and the second sealing projection 47 each have an annular shape and arearranged concentrically. The second sealing projection 47 is locatedradially outwardly of the first sealing projection 48. The size(diameter) of the second sealing projection 47 is larger than the size(diameter) of the first sealing projection 48. In a case of a face-downtype plating apparatus in which a substrate holder, holding a substratewith its to-be-plated surface facing downward, is disposed horizontallyin a plating tank, the second sealing projection 47 may be omitted.

When the second holding member 40 is secured to the first holding member38 by the coupling mechanism 41 with the back surface of the substrate Wsupported on the substrate support surface 38 a, the first sealingprojection 48 is pressed against a peripheral portion of the frontsurface (to-be-plated surface) of the substrate W, and the secondsealing projection 47 is pressed against the first holding member 38.The first sealing projection 48 seals a gap between the second holdingmember 40 and the front surface of the substrate W. and the secondsealing projection 47 seals a gap between the first holding member 38and the second holding member 40. Consequently, an internal space R isformed in the substrate holder 24.

The internal space R is formed by the first holding member 38, thesecond holding member 40 and the substrate W. The substrate holder 24has a plurality of electrical contacts 50 disposed in the internal spaceR. The electrical contacts 50 are disposed such that they contact theperipheral portion of the substrate W when the substrate W is held bythe substrate holder 24. The electrical contacts 50 are connected to aplurality of electrical wires 54 extending in the interior of the firstholding member 38. The electrical wires 54 are disposed in a wirepassage 55 formed in the first holding member 38. One ends of theelectrical wires 54 are connected to the electrical contacts 50, whilethe other ends of the electrical wires 54 are connected to an externalterminal 59 secured to the first holding member 38. When the substrateholder 24 is set in the plating tank 10 shown in FIG. 1, the externalterminal 59 is electrically connected to the power source 30 shown inFIG. 1.

One end of the wire passage 55 opens in a peripheral surface of thefirst holding member 38, while the other end of the wire passage 55communicates with the internal space R. The internal space Rcommunicates with the atmosphere through the wire passage 55.Accordingly, the atmospheric pressure is produced in the internal spaceR.

FIG. 3 is a schematic view showing an embodiment of a leak checkingapparatus 60 for testing the sealing performances of the first sealingprojection 48 and the second sealing projection 47 of the substrateholder 24. The test of the sealing performances of the first sealingprojection 48 and the second sealing projection 47 is performed bychecking whether a pressurized gas leaks through the sealing projections47, 48. This leak check is performed when the substrate holder 24 isholding the substrate W.

As shown in FIG. 3, the leak checking apparatus 60 includes a sealingcap 61 having a shape that covers the second holding member 40 of thesubstrate holder 24, a pressing mechanism 62 for pressing the sealingcap 61 against the first holding member 38 of the substrate holder 24,and a pressurized-gas supply system 63 coupled to the sealing cap 61.The pressing mechanism 62 may be, for example, an air cylinder or anelectric actuator. The sealing cap 61 is a rigid body which does notpermit passage of a gas, and has a larger size than an assembly of thesubstrate W and the second holding member 40. The sealing cap 61 has ashape that covers the opening 40 a of the second holding member 40, thefirst sealing projection 48, and the second sealing projection 47. Thesealing cap 61 has an endless gas seal 66 secured to an open end of thesealing cap 61. In this embodiment the gas seal 66 has an annular shape.

The sealing cap 61 is pressed against the substrate holder 24 by thepressing mechanism 62 with the gas seal 66 in contact with the firstholding member 38 of the substrate holder 24. The gas seal 66 is pressedagainst the first holding member 38 of the substrate holder 24 to seal agap between the sealing cap 61 and the first holding member 38, therebyforming a hermetic space S between the sealing cap 61 and the substrateholder 24. The hermetic space S is formed by the sealing cap 61, thefirst holding member 38 and the second holding member 40 of thesubstrate holder 24, and the front surface of the substrate W that isexposed through the opening 40 a of the second holding member 40. Thefront surface of the substrate W, exposed through the opening 40 a ofthe second holding member 40, the first sealing projection 48, and thesecond sealing projection 47 are covered by the sealing cap 61.

The pressurized-gas supply system 63 includes a pressurized-gasintroduction line 70 coupled to the sealing cap 61, adifferential-pressure check line 75 branching off from thepressurized-gas introduction line 70, and a bridge line 88 coupled toboth the pressurized-gas introduction line 70 and thedifferential-pressure check line 75. The leak checking apparatus 60includes a master container 80 coupled to the differential-pressurecheck line 75, and a differential-pressure measuring device 85 formeasuring a pressure difference between the pressurized gas in thehermetic space S and the pressurized gas in the master container 80. Themaster container 80 is a container in which no gas leak is guaranteed.The differential-pressure measuring device 85 is attached to the bridgeline 88, and communicates with both the hermetic space S and the mastercontainer 80. One end of the differential-pressure measuring device 85is coupled to the pressurized-gas introduction line 70 through thebridge line 88, while the other end of the differential-pressuremeasuring device 85 is coupled to the master container 80 through thebridge line 88 and the differential-pressure check line 75.

One end of the pressurized-gas introduction line 70 is coupled to apressurized-gas supply source 90, while the other end of thepressurized-gas introduction line 70 communicates with the hermeticspace S formed between the sealing cap 61 and the substrate holder 24.Therefore, the pressurized gas is supplied into the hermetic space Sthrough the pressurized-gas introduction line 70. Further, thepressurized gas is supplied into the master container 80 through thepressurized-gas introduction line 70 and the differential-pressure checkline 75. Examples of the pressurized gas may include nitrogen gas,helium gas, argon gas and carbon dioxide gas.

The pressurized-gas introduction line 70 is provided with a pressureregulator 93. The operation of the pressure regulator 93 is controlledby an operation controller 95. The pressure regulator 93 is a devicecapable of regulating the pressure of the pressurized gas in thepressurized-gas introduction line 70 based on a pressure command valuesent from the operation controller 95. An electropneumatic regulator canbe used as the pressure regulator 93. The pressure regulator 93 has apressure sensor (not shown) for measuring the pressure of thepressurized gas in the pressurized-gas introduction line 70. Theoperation controller 95 sends the pressure command value to the pressureregulator 93, and the pressure regulator 93 operates to maintain thepressurized gas in the pressurized-gas introduction line 70 at apressure corresponding to the pressure command value.

A holder-side exhaust line 97 and a master-side exhaust line 98 arecoupled to the pressurized-gas introduction line 70 and thedifferential-pressure check line 75, respectively. The pressurized-gassupply system 63 has a holder-side valve 101 attached to thepressurized-gas introduction line 70, a master-side valve 102 attachedto the differential-pressure check line 75, a first vent valve 103attached to the holder-side exhaust line 97, and a second vent valve 104attached to the master-side exhaust line 98. The holder-side valve 101and the master-side valve 102 are located upstream of the bridge line88. The holder-side exhaust line 97, the first vent valve 103, themaster-side exhaust line 98 and the second vent valve 104 are locateddownstream of the bridge line 88. The operations of the holder-sidevalve 101, the master-side valve 102, the first vent valve 103 and thesecond vent valve 104 are controlled by the operation controller 95.

When the operation controller 95 opens the holder-side valve 101 and themaster-side valve 102 while keeping the first vent valve 103 and thesecond vent valve 104 closed, the pressurized gas flows through thepressurized-gas introduction line 70 and the differential-pressure checkline 75, and is introduced into the hermetic space S and the mastercontainer 80. The pressure of the pressurized gas in the hermetic spaceS and that in the master container 80 are regulated by the pressureregulator 93, and the operation of the pressure regulator 93 iscontrolled by the operation controller 95.

When the holder-side valve 101 and the master-side valve 102 are closed,the hermetic space S and the master container 80 are sealed, so that thepressurized gas is confined in the hermetic space S and in the mastercontainer 80. The pressure of the pressurized gas in the sealed hermeticspace S is equal to the pressure of the pressurized gas in the sealedmaster container 80. However, if the sealing performance of the firstsealing projection 48 and/or the second sealing projection 47 hasdeteriorated, the pressurized gas in the hermetic space S leaks into theinternal space R of the substrate holder 24 through the first sealingprojection 48 and/or the second sealing projection 47. Consequently, thepressure in the hermetic space S decreases.

Therefore, in order to check the leakage of the pressurized gas from thehermetic space S, the leak checking apparatus 60 includes a pressuredecrease detector 81 for detecting a decrease in the pressure of thepressurized gas in the hermetic space S. More specifically, the pressuredecrease detector 81 measures a decrease in the pressure of thepressurized gas in the sealed hermetic space S, and determines whetherthe decrease in the pressure has exceeded a threshold value within a settime. In this embodiment, the pressure decrease detector 81 includes atleast the master container 80 and the differential-pressure measuringdevice 85. The pressure in the master container 80, which is a containerin which no gas leak is guaranteed, does not decrease over time.

The differential-pressure measuring device 85 is configured to measure apressure difference between the pressurized gas in the hermetic space Sand the pressurized gas in the master container 80. This pressuredifference corresponds to the decrease in the pressure of thepressurized gas in the hermetic space S. Further, thedifferential-pressure measuring device 85 compares the pressuredifference to the threshold value, and determines whether the pressuredifference has exceeded the threshold value within the set time. Thedifferential-pressure measuring device 85 is configured to emit a signalindicating that there is no leakage of the pressurized gas (i.e. thefirst sealing projection 48 and the second sealing projection 47 arefunctioning properly) if the pressure difference has not exceeded thethreshold value within the set time, and to emit a signal indicatingthat there is leakage of the pressurized gas (i.e. there is a failure ofthe first sealing projection 48 and/or the second sealing projection 47)if the pressure difference has exceeded the threshold value within theset time. The set time may be in the range of 1 second to 30 seconds,preferably in the range of 2 to 10 seconds. In an embodiment, thepressure decrease detector 81 may measure the pressure of thepressurized gas in the hermetic space S with a pressure sensor (notshown), and detect whether the measured pressure has become lower than athreshold value within a set time.

According to this embodiment, the pressure of the pressurized gas isapplied to the substrate W and the substrate holder 24 during the leakcheck operation. During plating of the substrate W, the pressure of theplating solution is applied to the substrate W and the substrate holder24 as well. In particular, the substrate W is pressed by the platingsolution in a direction away from the first sealing projection 48. Theleak check using the pressurized gas is performed under conditionssimilar to conditions under which the substrate W is immersed in theplating solution. Therefore, the leak check according to this embodimentcan check the sealing performances of the first sealing projection 48and the second sealing projection 47 more accurately than conventionalleak check using vacuum pressure.

In order to perform the leak check under the conditions similar to theconditions under which the substrate W is immersed in the platingsolution, the pressure of the pressurized gas may preferably be equal tothe pressure of the plating solution applied to the first sealingprojection 48 and the second sealing projection 47 during plating of thesubstrate W. The pressure of the pressurized gas is determined inadvance from this viewpoint, and the operation controller 95 controlsthe operation of the pressure regulator 93 so that the pressurized gashas the determined pressure.

As shown in FIG. 1, the substrate holder 24 and the substrate W areimmersed in a vertical position in the plating solution. Accordingly,there is a difference in the pressure of the plating solution between anupper portion and a lower portion of the substrate holder 24. In thisembodiment, the lowest pressure of the plating solution acts on theuppermost portion of the second sealing projection 47, while the highestpressure of the plating solution acts on the lowermost portion of thesecond sealing projection 47. In a case where the diameter of the firstsealing projection 48 is larger than the diameter of the second sealingprojection 47, the lowest pressure of the plating solution acts on theuppermost portion of the first sealing projection 48, while the highestpressure of the plating solution acts on the lowermost portion of thefirst sealing projection 48.

In the following descriptions, the pressure of the plating solutionapplied to the uppermost portion of the second sealing projection 47 isreferred to as pressure P1, and the pressure of the plating solutionapplied to the lowermost portion of the second sealing projection 47 isreferred to as pressure P2. In an embodiment, the pressure P1 may be thepressure of the plating solution applied to the uppermost portion of thefirst sealing projection 48, and the pressure P2 may be the pressure ofthe plating solution applied to the lowermost portion of the firstsealing projection 48.

The pressures P1, P2 depend on the size of the substrate holder 24, thediameter of the substrate W, the diameter of the second sealingprojection 47 (or the first sealing projection 48), and a surface levelof the plating solution held in the plating tank 10. The platingsolution overflows the side wall of the plating tank 10 into theoverflow tank 12; therefore, the surface level of the plating solutioncoincides with the position of the top of the side wall of the platingtank 10.

A pressure of the pressurized gas, to be used in the leak check, isdetermined based on the pressure P1 and the pressure P2 which can beapplied from the plating solution to the second sealing projection 47(or the first sealing projection 48) during plating of the substrate W.In an embodiment, the pressure of the pressurized gas is not less thanthe pressure P1 and not more than the pressure P2. The pressure of thepressurized gas may be higher than the pressure P2. A preset pressurerange is pre-stored in the operation controller 95. The pressure rangeincludes a pressure of the plating solution which is expected to beapplied to the first sealing projection 48 and the second sealingprojection 47 when the substrate W, held by the substrate holder 24, isimmersed in the plating solution held in the plating tank 10. In anembodiment, the lower limit of the pressure range is the pressure P1,while the upper limit is a numerical value obtained by multiplying thevalue of the pressure P2 by a factor which is a predetermined value ofnot less than 1.

The operation controller 95 sends a pressure command value, which hasbeen selected from the pressure range, to the pressure regulator 93, andthe pressure regulator 93 operates to maintain the pressurized gas inthe pressurized-gas introduction line 70 at a pressure corresponding tothe pressure command value. In an embodiment, the pressure command valueis the value of the pressure P2. In this case, the pressurized gassupplied to the hermetic space S has the pressure P2 which correspondsto the maximum pressure that can be applied from the plating solution tothe second sealing projection 47. The leak check is thus performed underthe realistic and unfavorable conditions. In other words, the substrateholder 24, having the first sealing projection 48 and the second sealingprojection 47 that have passed the leak check, is highly reliable.Therefore, according to this embodiment, plating of the substrate W canbe performed with the use of the highly reliable substrate holder 24.

A leak checking method performed by using the above-described leakchecking apparatus 60 will now be described with reference to FIG. 4.First, the substrate W is interposed between the first holding member 38and the second holding member 40 with the front surface of the substrateW exposed through the opening 40 a of the second holding member 40,whereby the substrate W is held by the substrate holder 24 (step 1).When holding the substrate W with the substrate holder 24, the firstsealing projection 48 of the second holding member 40 seals the gapbetween the peripheral portion of the front surface of the substrate Wand the second holding member 40, and the second sealing projection 47of the second holding member 40 seals the gap between the first holdingmember 38 and the second holding member 40, thereby forming the internalspace R in the substrate holder 24 by the first holding member 38, thesecond holding member 40 and the substrate W.

Next, the sealing cap 61 is disposed on the first holding member 38 ofthe substrate holder 24 so as to cover the entireties of the frontsurface of the substrate W, exposed through the opening 40 a, and thesecond holding member 40 (step 2). The gas seal 66 of the sealing cap 61is pressed against the first holding member 38 by the pressing mechanism62 to seal the gap between the first holding member 38 and the sealingcap 61, thereby forming the hermetic space S between the sealing cap 61and the substrate holder 24 (step 3).

The operation controller 95 selects a pressure command value from thepressure range stored therein, and sends the pressure command value tothe pressure regulator 93 (step 4). The operation controller 95 opensthe holder-side valve 101 and the master-side valve 102 while keepingthe first vent valve 103 and the second vent valve 104 closed. Thepressurized gas flows through the pressurized-gas introduction line 70and the differential-pressure check line 75 into the hermetic space Sand the master container 80 (step 5). The pressure of the pressurizedgas in the hermetic space S and in the master container 80 is regulatedby the pressure regulator 93, and the operation of the pressureregulator 93 is controlled by the operation controller 95. Morespecifically, the pressure regulator 93 operates to maintain thepressurized gas in the pressurized-gas introduction line 70 at apressure corresponding to the pressure command value.

When a predetermined amount of time has elapsed since the holder-sidevalve 101 and the master-side valve 102 were opened, the operationcontroller 95 closes the holder-side valve 101 and the master-side valve102. The hermetic space S and the master container 80 are sealed by theholder-side valve 101 and the master-side valve 102, respectively. Thehermetic space S and the master container 80 are each filled with thepressurized gas having the same pressure (step 6).

As described above, with the holder-side valve 101 and the master-sidevalve 102 closed, the differential-pressure measuring device 85 measuresa pressure difference between the pressurized gas in the hermetic spaceS and the pressurized gas in the master container 80 (step 7). Thedifferential-pressure measuring device 85 determines whether thepressure difference has exceeded the threshold value within the set time(step 8). If the pressure difference has not exceeded the thresholdvalue within the set time, the differential-pressure measuring device 85emits a signal indicating that there is no leakage of the pressurizedgas in the hermetic space S (i.e. the first sealing projection 48 andthe second sealing projection 47 are functioning properly) (step 9). Ifthe pressure difference has exceeded the threshold value within the settime, the differential-pressure measuring device 85 emits a signalindicating that there is leakage of the pressurized gas in the hermeticspace S (i.e. there is a failure of the first sealing projection 48and/or the second sealing projection 47) (step 10).

The operation controller 95 opens the first vent valve 103 and thesecond vent valve 104, so that the pressurized gas in the hermetic spaceS and the pressurized gas in the master container 80 are dischargedthrough the holder-side exhaust line 97 and the master-side exhaust line98. The leak check is performed in this manner to test the sealingperformances of the first sealing projection 48 and the second sealingprojection 47.

In some cases, the leak check is performed on a substrate holder whichhas a substrate support surface 38 a configured to contact the back sideof a peripheral portion of a substrate W to support the substrate W.When the substrate W is held by the substrate holder, a space is formedon the back surface of the substrate W, and the space on the backsurface communicates with the internal space R. If the pressurized gasis not supplied to the space on the back surface of the substrate W andis supplied only to the hermetic space S on the front surface of thesubstrate W in the leak check for the substrate holder, then there is afear that the substrate W will warp. Therefore, it is preferred tosupply the pressurized gas to the internal space R so that the pressurein the internal space R becomes higher than the atmospheric pressureand, in addition, becomes lower than or substantially equal to thepressure in the hermetic space S on the front surface of the substrateW. This can prevent or reduce warping of the substrate W upon the leakcheck.

FIG. 5 is a schematic view showing another embodiment of a leak checkingapparatus 60. The constructions of this embodiment, not particularlydescribed here, are the same as the constructions of the embodimentdescribed above with reference to FIG. 3, and duplicate descriptionsthereof are omitted.

In this embodiment, the sealing cap 61 further has an endless partitionseal 109 which contacts the second holding member 40 when the gas seal66 contacts the first holding member 38 of the substrate holder 24. Inthis embodiment, as with the gas seal 66, the partition seal 109 has anannular shape. The partition seal 109 is disposed radially inwardly ofthe gas seal 66; the size (diameter) of the partition seal 109 issmaller than the size (diameter) of the gas seal 66. In this embodiment,the size (diameter) of the partition seal 109 is larger than that of thefirst sealing projection 48 and smaller than that of the second sealingprojection 47.

When the pressing mechanism 62 presses the sealing cap 61 against thesubstrate holder 24, the gas seal 66 of the sealing cap 61 is pressedagainst the first holding member 38, and the partition seal 109 of thesealing cap 61 is pressed against the second holding member 40.Consequently, the hermetic space S, formed between the substrate holder24 and the sealing cap 61, is divided by the partition seal 109 into afirst hermetic space S1 and a second hermetic space S2. The firsthermetic space S1 is located inside the second hermetic space S2.

The first hermetic space S1 is partly defined by the partition seal 109and the first sealing projection 48, while the second hermetic space S2is partly defined by the gas seal 66, the partition seal 109 and thesecond sealing projection 47. In other words, the first sealingprojection 48 of the substrate holder 24 faces the first hermetic spaceS1, while the second sealing projection 47 of the substrate holder 24faces the second hermetic space S2. Therefore, in the event of a failureof the first sealing projection 48, the pressurized gas in the firsthermetic space S1 leaks into the internal space R In the event of afailure of the second sealing projection 47, the pressurized gas in thesecond hermetic space S2 leaks into the internal space R.

The pressurized-gas introduction line 70 branches into a first branchline 11 and a second branch line 112. The first branch line 111 and thesecond branch line 112 are located downstream of the bridge line 88.Both of the two branch lines 111, 112 are coupled to the sealing cap 61.The first branch line 111 communicates with the first hermetic space S1,and the second branch line 112 communicates with the second hermeticspace S2. The first branch line 111 is provided with a first branchvalve 113, and the second branch line 112 is provided with a secondbranch valve 114. By opening either the first branch valve 113 or thesecond branch valve 114, the pressurized gas can be supplied selectivelyto the first hermetic space S1 or the second hermetic space S2. Theoperations of the first branch valve 113 and the second branch valve 114are controlled by the operation controller 95. The operation controller95 is configured to be capable of manipulating the first branch valve113 and the second branch valve 114 independently of each other.

An embodiment of a leak checking method, performed by using the leakchecking apparatus 60 shown in FIG. 5, will now be described withreference to FIGS. 6 and 7. First, the substrate W is interposed betweenthe first holding member 38 and the second holding member 40 with thefront surface of the substrate W exposed through the opening 40 a of thesecond holding member 40, whereby the substrate W is held by thesubstrate holder 24 (step 1). When holding the substrate W with thesubstrate holder 24, the first sealing projection 48 of the secondholding member 40 seals the gap between the peripheral portion of thefront surface of the substrate W and the second holding member 40, andthe second sealing projection 47 of the second holding member 40 sealsthe gap between the first holding member 38 and the second holdingmember 40, thereby forming the internal space R in the substrate holder24 by the first holding member 38, the second holding member 40 and thesubstrate W.

Next, the sealing cap 61 is disposed on the first holding member 38 ofthe substrate holder 24 so as to cover the entireties of the frontsurface of the substrate W, exposed through the opening 40 a, and thesecond holding member 40 (step 2). The gas seal 66 of the sealing cap 61is pressed against the first holding member 38 by the pressing mechanism62 to seal the gap between the first holding member 38 and the sealingcap 61, thereby forming a hermetic space between the sealing cap 61 andthe substrate holder 24 (step 3). At the same time, the partition seal109 of the sealing cap 61 is pressed against the second holding member40 by the pressing mechanism 62, whereby the hermetic space is dividedby the partition seal 109 into the first hermetic space S1 and thesecond hermetic space S2 (step 4).

The operation controller 95 selects a pressure command value from thepressure range stored therein, and sends the pressure command value tothe pressure regulator 93 (step 5). The operation controller 95 opensthe holder-side valve 101, the master-side valve 102 and the firstbranch valve 113 while keeping the first vent valve 103, the second ventvalve 104 and the second branch valve 114 closed. The pressurized gasflows through the pressurized-gas introduction line 70 and thedifferential-pressure check line 75 into the first hermetic space S1 andthe master container 80 (step 6). The pressure regulator 93 operates tomaintain the pressurized gas in the first hermetic space S and thepressurized gas in the master container 80 at a pressure correspondingto the pressure command value.

With the recent progress of three-dimensional packaging technology orWLP (Wafer Level Packaging) technology, electroplating of a thin-filmsubstrate is being studied. Thus, the substrate W can be a thin-filmsubstrate e.g. having a maximum thickness of 400 μm. In order to preventsuch a substrate W from being warped or damaged by a fluid pressureapplied to the substrate W when the pressurized gas is supplied to thefirst hermetic space S1, the first branch valve 113 for supplying thepressurized gas to the first hermetic space S is preferably located at aposition which is not close to but distant from the substrate W. Thisenables the leak check to be performed on the substrate holder 24 evenwhen it is holding such a thin-film substrate.

When a predetermined amount of time has elapsed since the holder-sidevalve 101, the master-side valve 102 and the first branch valve 113 wereopened, the operation controller 95 closes the holder-side valve 101 andthe master-side valve 102. The first hermetic space S1 and the mastercontainer 80 are sealed by the holder-side valve 101 and the master-sidevalve 102, respectively. The first hermetic space S1 and the mastercontainer 80 are each filled with the pressurized gas having the samepressure (step 7).

With the holder-side valve 101 and the master-side valve 102 closed, thedifferential-pressure measuring device 85 measures a pressure differencebetween the pressurized gas in the first hermetic space S1 and thepressurized gas in the master container 80 (step 8). Thedifferential-pressure measuring device 85 determines whether thepressure difference has exceeded a threshold value within the set time(step 9). If the pressure difference has not exceeded the thresholdvalue within the set time, the differential-pressure measuring device 85emits a signal indicating that there is no leakage of the pressurizedgas in the first hermetic space S1 (i.e. the first sealing projection 48is functioning properly) (step 10). If the pressure difference hasexceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas in the first hermetic space S1(i.e. there is a failure of the first sealing projection 48) (step 11).

The operation controller 95 opens the first vent valve 103 and thesecond vent valve 104 to discharge the pressurized gas in the firsthermetic space S and the pressurized gas in the master container 80through the holder-side exhaust line 97 and the master-side exhaust line98. The first leak check is performed in this manner to test the sealingperformance of the first sealing projection 48.

Subsequently, the second leak check for testing the sealing performanceof the second sealing projection 47 is performed in the followingmanner. The operation controller 95 opens the holder-side valve 101, themaster-side valve 102 and the second branch valve 114 while keeping thefirst vent valve 103, the second vent valve 104 and the first branchvalve 113 closed. The pressurized gas flows through the pressurized-gasintroduction line 70 and the differential-pressure check line 75 intothe second hermetic space S2 and the master container 80 (step 12, seeFIG. 7). The pressure regulator 93 operates to maintain the pressurizedgas in the second hermetic space S2 and the pressurized gas in themaster container 80 at a pressure corresponding to the pressure commandvalue.

When a predetermined amount of time has elapsed since the holder-sidevalve 101, the master-side valve 102 and the second branch valve 114were opened, the operation controller 95 closes the holder-side valve101 and the master-side valve 102. The second hermetic space S2 and themaster container 80 are sealed by the holder-side valve 101 and themaster-side valve 102, respectively. The second hermetic space S2 andthe master container 80 are each filled with the pressurized gas havingthe same pressure (step 13).

With the holder-side valve 101 and the master-side valve 102 closed, thedifferential-pressure measuring device 85 measures a pressure differencebetween the pressurized gas in the second hermetic space S2 and thepressurized gas in the master container 80 (step 14). Thedifferential-pressure measuring device 85 determines whether thepressure difference has exceeded a threshold value within the set time(step 15). If the pressure difference has not exceeded the thresholdvalue within the set time, the differential-pressure measuring device 85emits a signal indicating that there is no leakage of the pressurizedgas in the second hermetic space S2 (i.e. the second sealing projection47 is functioning properly) (step 16). If the pressure difference hasexceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas in the second hermetic space S2(i.e. there is a failure of the second sealing projection 47) (step 17).

The operation controller 95 opens the first vent valve 103 and thesecond vent valve 104 to discharge the pressurized gas in the secondhermetic space S2 and the pressurized gas in the master container 80through the holder-side exhaust line 97 and the master-side exhaust line98. The second leak check is performed in this manner to test thesealing performance of the second sealing projection 47.

Although in this embodiment the pressurized gas is first introduced intothe first hermetic space S1 and then into the second hermetic space S2,it is possible to first introduce the pressurized gas into the secondhermetic space S2 and then into the first hermetic space S1. In eithercase, in the event of gas leakage, it is possible to identify which ofthe first sealing projection 48 and the second sealing projection 47 hasa failure.

Another embodiment of the substrate holder 24 will now be described withreference to FIG. 8. The constructions of this embodiment, notparticularly described here, are the same as the constructions of thesubstrate holder 24 shown in FIG. 2, and duplicate descriptions thereofare omitted. As shown in FIG. 8, the first holding member 38 of thesubstrate holder 24 has an opening 38 b which is smaller than the backsurface of the substrate W. In this embodiment, the opening 38 b has acircular shape, and its diameter is smaller than the diameter of thesubstrate W. The size (diameter) of the opening 38 b of the firstholding member 38 is equal to the size (diameter) of the opening 40 a ofthe second holding member 40. The first holding member 38 has an endlessback-side sealing projection 49 which can contact the peripheral portionof the back surface of the substrate W. The back-side sealing projection49 may be a sealing member such as an O-ring. In an embodiment, a partof the first holding member 38 itself, including the back-side sealingprojection 49, may be formed of a material having a sealing function. Inthis embodiment, the back-side sealing projection 49 has an annularshape. The back-side sealing projection 49 has the same size (diameter)as the first sealing projection 48 of the second holding member 40 andis arranged concentrically with the first sealing projection 48.

When the substrate W is held by the substrate holder 24, the backsurface of the substrate W is exposed through the opening 38 b of thefirst holding member 38, and the front surface (to-be-plated surface) ofthe substrate W is exposed through the opening 40 a of the secondholding member 40. Further, the back-side sealing projection 49, thesecond sealing projection 47 and the first sealing projection 48 arepressed against the peripheral portion of the back surface of thesubstrate W, the first holding member 38 and the peripheral portion ofthe front surface of the substrate W, respectively. The back-sidesealing projection 49 seals a gap between the first holding member 38and the back surface of the substrate W, the second sealing projection47 seals the gap between the first holding member 38 and the secondholding member 40, and the first sealing projection 48 seals the gapbetween the second holding member 40 and the front surface of thesubstrate W. Consequently, an internal space R is formed in thesubstrate holder 24. The back-side sealing projection 49, the firstsealing projection 48 and the second sealing projection 47 face theinternal space R. This internal space R communicates with the atmospherethrough the wire passage 55. Accordingly, the atmospheric pressure isproduced in the internal space R.

In an embodiment, the sealing performances of the first sealingprojection 48, the second sealing projection 47 and the back-sidesealing projection 49 of the substrate holder 24 shown in FIG. 8 aretested using the leak checking apparatus 60 shown in FIG. 3. FIG. 9 is adiagram showing a manner in which the sealing performances of the firstsealing projection 48 and the second sealing projection 47 are tested byusing the leak checking apparatus 60 shown in FIG. 3. The sealingperformance test for the first sealing projection 48 and the secondsealing projection 47 is performed in accordance with the flow chartshown in FIG. 4. Thus, the sealing cap 61 is disposed on the firstholding member 38 of the substrate holder 24 such that the sealing cap61 covers the entireties of the front surface of the substrate W,exposed through the opening 40 a, and the second holding member 40, andthen the gas seal 66 of the sealing cap 61 is pressed against the firstholding member 38 by the pressing mechanism 62, thereby forming afront-side hermetic space S between the sealing cap 61 and the substrateholder 24. The front-side hermetic space S corresponds to the hermeticspace S in the above-described embodiment.

The test of the sealing performances of the first sealing projection 48and the second sealing projection 47 is performed by checking whetherthe pressurized gas in the front-side hermetic space S leaks through thesealing projections 47, 48. The pressurized-gas supply system 63supplies the pressurized gas at the same pressure to the front-sidehermetic space S and to the master container 80. If the pressuredifference between the pressurized gas in the front-side hermetic spaceS and the pressurized gas in the master container 80 has not exceeded athreshold value within the set time, the differential-pressure measuringdevice 85 emits a signal indicating that there is no leakage of thepressurized gas (i.e. the first sealing projection 48 and the secondsealing projection 47 are functioning properly). If the pressuredifference has exceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas (i.e. there is a failure of thefirst sealing projection 48 and/or the second sealing projection 47).

FIG. 10 is a diagram showing a manner in which the sealing performanceof the back-side sealing projection 49 is tested by using the leakchecking apparatus 60 shown in FIG. 3. The seal performance test for theback-side sealing projection 49 is performed on the substrate holder 24with its back side facing the sealing cap 61. As shown in FIG. 10, thesealing cap 61 is disposed on the first holding member 38 of thesubstrate holder 24 such that the sealing cap 61 covers the back surfaceof the substrate W exposed through the opening 38 b. While the gas seal66 is in contact with the back surface of the first holding member 38,the sealing cap 61 is pressed against the substrate holder 24 by thepressing mechanism 62. The gas seal 66 is pressed against the backsurface of the first holding member 38 to seal a gap between the sealingcap 61 and the first holding member 38, thereby forming a back-sidehermetic space U between the sealing cap 61 and the substrate holder 24.

The back-side hermetic space U is formed by the sealing cap 61, thefirst holding member 38 of the substrate holder 24, and the back surfaceof the substrate W exposed through the opening 38 b of the first holdingmember 38. The exposed back surface of the substrate W and the back-sidesealing projection 49 are covered by the sealing cap 61, and face theback-side hermetic space U. As with the sealing performance test for thesealing projections 47, 48, the test of the sealing performance of theback-side sealing projection 49 is performed by checking whether thepressurized gas in the back-side hermetic space U leaks through theback-side sealing projection 49.

The sealing performance test for the back-side sealing projection 49 isperformed by following the flow chart shown in FIG. 4 (except step 1).Specifically, the sealing cap 61 is disposed on the first holding member38 of the substrate holder 24 such that the sealing cap 61 covers theentirety of the back surface of the substrate W exposed through theopening 38 b. The gas seal 66 of the sealing cap 61 is pressed againstthe back surface of the first holding member 38 by the pressingmechanism 62, thereby forming the back-side hermetic space U between thesealing cap 61 and the substrate holder 24. The pressurized-gas supplysystem 63 supplies the pressurized gas at the same pressure into theback-side hermetic space U and into the master container 80. If thepressure difference between the pressurized gas in the back-sidehermetic space U and the pressurized gas in the master container 80 hasnot exceeded a threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is no leakage of the pressurized gas (i.e. the back-side sealingprojection 49 is functioning properly). If the pressure difference hasexceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas (i.e. there is a failure of theback-side sealing projection 49).

FIG. 11 is a flow chart of the leak check for the second sealingprojection 47, the first sealing projection 48 and the back-side sealingprojection 49 of the substrate holder 24, shown in FIGS. 9 and 10.First, the test of the sealing performances of the first sealingprojection 48 and the second sealing projection 47 is performed byfollowing the flow chart shown in FIG. 4 (step 1). The step 1 isperformed in the state illustrated in FIG. 9. Next, the substrate holder24 is reversed (step 2). The test of the sealing performance of theback-side sealing projection 49 is then performed by following the flowchart shown in FIG. 4 (except the step 1 of FIG. 4) (step 3). This step3 is performed in the state illustrated in FIG. 10.

A description will now be given of an embodiment in which a leak checkfor the first sealing projection 48, the second sealing projection 47and the back-side sealing projection 49 of the substrate holder 24 shownin FIG. 8 is performed by using the leak checking apparatus 60 shown inFIG. 5. FIG. 12 is a diagram showing a manner in which the sealingperformances of the first sealing projection 48 and the second sealingprojection 47 are tested by using the leak checking apparatus 60 shownin FIG. 5. The test to determine whether the pressurized gas leaksthrough the first sealing projection 48 and the second sealingprojection 47 is performed by following the flow chart shown in FIGS. 6and 7. Specifically, the sealing cap 61 is disposed on the first holdingmember 38 of the substrate holder 24 such that the sealing cap 61 coversthe entireties of the front surface of the substrate W, exposed throughthe opening 40 a, and the second holding member 40. The pressingmechanism 62 presses the gas seal 66 and the partition seal 109 againstthe first holding member 38 and the second holding member 40,respectively, thereby forming a first hermetic space S1 and a secondhermetic space S2 between the sealing cap 61 and the substrate holder24. These first hermetic space S and second hermetic space S2 correspondto the first hermetic space S1 and the second hermetic space S2 in theabove-described embodiment.

The pressurized-gas supply system 63 supplies the pressurized gas at thesame pressure into the first hermetic space S1 and into the mastercontainer 80. If the pressure difference between the pressurized gas inthe first hermetic space S1 and the pressurized gas in the mastercontainer 80 has not exceeded a threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is no leakage of the pressurized gas (i.e. the first sealingprojection 48 is functioning properly). If the pressure difference hasexceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas (i.e. there is a failure of thefirst sealing projection 48).

Subsequently, the pressurized-gas supply system 63 supplies thepressurized gas at the same pressure to the second hermetic space S2 andto the master container 80. If the pressure difference between thepressurized gas in the second hermetic space S2 and the pressurized gasin the master container 80 has not exceeded a threshold value within theset time, the differential-pressure measuring device 85 emits a signalindicating that there is no leakage of the pressurized gas (i.e. thesecond sealing projection 47 is functioning properly). If the pressuredifference has exceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas (i.e. there is a failure of thesecond sealing projection 47).

FIG. 13 is a diagram showing a manner in which the sealing performanceof the back-side sealing projection 49 is tested by using the leakchecking apparatus 60 shown in FIG. 5. The test to determine whether thepressurized gas leaks through the back-side sealing projection 49 isperformed by following the flow chart shown in FIG. 4 (except step 1).Specifically, the sealing cap 61 is disposed on the first holding member38 of the substrate holder 24 such that the sealing cap 61 covers theentirety of the back surface of the substrate W exposed through theopening 38 b, and then the gas seal 66 of the sealing cap 61 is pressedagainst the back surface of the first holding member 38 by the pressingmechanism 62, thereby forming the back-side hermetic space U between thesealing cap 61 and the substrate holder 24.

The pressurized-gas supply system 63 supplies the pressurized gas at thesame pressure into the back-side hermetic space U and into the mastercontainer 80. If the pressure difference between the pressurized gas inthe back-side hermetic space U and the pressurized gas in the mastercontainer 80 has not exceeded a threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is no leakage of the pressurized gas (i.e. the back-side sealingprojection 49 is functioning properly). If the pressure difference hasexceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas (i.e. there is a failure of theback-side sealing projection 49). One or both of the first branch line111 and the second branch line 112 may be used in this test. The leakcheck can be performed in a shorter time by increasing the pressure ofthe pressurized gas itself in the master container 80.

FIG. 14 is a flow chart showing the leak check for the first sealingprojection 48, the second sealing projection 47 and the back-sidesealing projection 49 of the substrate holder 24, shown in FIGS. 12 and13. First, the test of the sealing performances of the first sealingprojection 48 and the second sealing projection 47 is performed byfollowing the flow chart shown in FIGS. 6 and 7 (step 1 and step 2).These steps 1 and 2 are performed in the state illustrated in FIG. 12.The seal performance test may be first performed on the second sealingprojection 47 and then on the first sealing projection 48. Next, thesubstrate holder 24 is reversed (step 3). The test of the sealingperformance of the back-side sealing projection 49 is then performed byfollowing the flow chart shown in FIG. 4 (except the step 1 of FIG. 4)(step 4). This step 4 is performed in the state illustrated in FIG. 13.Instead of reversing the substrate holder 24, the leak checkingapparatus 60 may be moved or reversed in step 3.

Another embodiment of the substrate holder 24 will now be described withreference to FIG. 15. The constructions of this embodiment, notparticularly described here, are the same as the constructions of thesubstrate holder 24 shown in FIG. 8, and duplicate descriptions thereofare omitted. The substrate holder 24 shown in FIG. 15 includes a firstholding member 38 and a second holding member 40 which have the samesize. A coupling mechanism 41 is mounted on the outer surfaces of thefirst holding member 38 and the second holding member 40. A substrate Wis interposed between the first holding member 38 and the second holdingmember 40, and then the first holding member 38 and the second holdingmember 40 are secured to each other by the coupling mechanism 41,whereby the substrate W is held by the substrate holder 24.

The first holding member 38 has an endless back-side sealing projection49 which can contact a peripheral portion of the back surface of thesubstrate W. In this embodiment, the back-side sealing projection 49 hasan annular shape. The first holding member 38 also has an endlessintermediate sealing member 116 for sealing a gap between the firstholding member 38 and the second holding member 40. This intermediatesealing member 116 corresponds to the second sealing projection 47 inthe above-described embodiment. In an embodiment, the intermediatesealing member 116 may be provided on the second holding member 40.

The second holding member 40 has an endless front-side sealingprojection 117 which can contact a peripheral portion of the frontsurface of the substrate W. The front-side sealing projection 117corresponds to the first sealing projection 48 in the above-describedembodiment. In this embodiment, the front-side sealing projection 117has an annular shape. The back-side sealing projection 49 has the samesize (diameter) as the front-side sealing projection 117 and is arrangedconcentrically with the front-side sealing projection 117. Thefront-side sealing projection 117 may be a sealing member such as anO-ring. In an embodiment, the second holding member 40 itself, includingthe front-side sealing projection 117, may be formed of a materialhaving a sealing function.

When the substrate W is held by the substrate holder 24, the backsurface of the substrate W is exposed through the opening 38 b of thefirst holding member 38, and the front surface (to-be-plated surface) ofthe substrate W is exposed through the opening 40 a of the secondholding member 40. Further, the back-side sealing projection 49, thefront-side sealing projection 117 and the intermediate sealing member116 are pressed against a peripheral portion of the back surface of thesubstrate W, a peripheral portion of the front surface of the substrateW and the second holding member 40, respectively. The back-side sealingprojection 49 seals the gap between the first holding member 38 and theback surface of the substrate W, the front-side sealing projection 117seals the gap between the second holding member 40 and front surface ofthe substrate W, and the intermediate sealing member 116 seals the gapbetween the first holding member 38 and the second holding member 40.Consequently, an internal space R is formed in the substrate holder 24.The back-side sealing projection 49 and the front-side sealingprojection 117 face the internal space R. This internal space Rcommunicates with the atmosphere through the wire passage 55.Accordingly, the atmospheric pressure is produced in the internal spaceR.

The first holding member 38 includes a plurality of positioning members115 which contact an edge portion of the substrate W. The position ofthe substrate W relative to the substrate holder 24 is fixed by thepositioning members 115. In an embodiment, the second holding member 40may include the positioning members 115.

FIG. 16 is a diagram showing an embodiment of a leak checking apparatus60 for performing a leak check on the front-side sealing projection 117and the back-side sealing projection 49 of the substrate holder 24 shownin FIG. 15. The constructions of the leak checking apparatus 60 of thisembodiment, not particularly described here, are the same as theconstructions of the leak checking apparatus 60 shown in FIG. 3, andduplicate descriptions thereof are omitted. The leak checking apparatus60 of this embodiment includes a front-side sealing cap 119 to bedisposed on the front side of the substrate holder 24, and a back-sidesealing cap 120 to be disposed on the back side of the substrate holder24.

Each of the front-side sealing cap 119 and the back-side sealing cap 120is a rigid body which does not permit passage of a gas, and has a largersize than the substrate W. The front-side sealing cap 119 has a shapewhich is larger than the opening 40 a of the second holding member 40and which can cover the opening 40 a and the front-side sealingprojection 117. The back-side sealing cap 120 has a shape which islarger than the opening 38 b of the first holding member 38 and whichcan cover the opening 38 b and the back-side sealing projection 49.

The front-side sealing cap 119 has an endless front-side gas seal 121.In this embodiment, the front-side gas seal 121 has an annular shape.The front-side gas seal 121 is larger than the opening 40 a of thesecond holding member 40. That is to say, the front-side gas seal 121has a diameter larger than the diameter of the opening 40 a of thesecond holding member 40. The front-side sealing cap 119 is coupled to apressing mechanism 62 comprised of an air cylinder, an electricactuator, or the like. The pressing mechanism 62 is configured to pressthe front-side gas seal 121 of the front-side sealing cap 119 againstthe front surface of the second holding member 40. The gap between thefront-side sealing cap 119 and the second holding member 40 is sealedwith the front-side gas seal 121, whereby a front-side hermetic space Sis formed between the front-side sealing cap 119 and the front side ofthe substrate holder 24. This front-side hermetic space S corresponds tothe hermetic space S in the above-described embodiment.

The back-side sealing cap 120 has an endless back-side gas seal 122. Inthis embodiment, the back-side gas seal 122 has an annular shape. Theback-side gas seal 122 is larger than the opening 38 b of the firstholding member 38. That is to say, the back-side gas seal 122 has adiameter larger than the diameter of the opening 38 b of the firstholding member 38. The back-side sealing cap 120 is coupled to apressing mechanism 130 comprised of an air cylinder, an electricactuator, or the like. The pressing mechanism 130 is configured to pressthe back-side gas seal 122 of the back-side sealing cap 120 against theback surface of the first holding member 38. The gap between theback-side sealing cap 120 and the first holding member 38 is sealed withthe back-side gas seal 122, whereby a back-side hermetic space U isformed between the back-side sealing cap 120 and the back side of thesubstrate holder 24.

The pressurized-gas introduction line 70 branches into a front-sidebranch line 125 and a back-side branch line 128. The front-side branchline 125 and the back-side branch line 128 are located downstream of thebridge line 88. The front-side branch line 125 is coupled to thefront-side sealing cap 119, and the back-side branch line 128 is coupledto the back-side sealing cap 120. The front-side branch line 125communicates with the front-side hermetic space S, and the back-sidebranch line 128 communicates with the back-side hermetic space U.

The front-side branch line 125 is provided with a front-side branchvalve 126, and the back-side branch line 128 is provided with aback-side branch valve 129. By opening the front-side branch valve 126and/or the back-side branch valve 129, the pressurized gas can besupplied into the front-side hermetic space S and/or the back-sidehermetic space U. The operations of the front-side branch valve 126 andthe back-side branch valve 129 are controlled by the operationcontroller 95. In particular, the operation controller 95 is configuredto be capable of manipulating the front-side branch valve 126 and theback-side branch valve 129 independently of each other.

The front-side hermetic space S is formed by the front-side sealing cap119, the second holding member 40 of the substrate holder 24, and thefront surface of the substrate W exposed through the opening 40 a of thesecond holding member 40. The exposed front surface of the substrate Wand the front-side sealing projection 117 are covered by the front-sidesealing cap 119, and face the front-side hermetic space S. The test ofthe sealing performance of the front-side sealing projection 117 isperformed by checking whether the pressurized gas in the front-sidehermetic space S leaks through the front-side sealing projection 117.

The back-side hermetic space U is formed by the back-side sealing cap120, the first holding member 38 of the substrate holder 24, and theback surface of the substrate W exposed through the opening 38 b of thefirst holding member 38. The exposed back surface of the substrate W andthe back-side sealing projection 49 are covered by the back-side sealingcap 120, and face the back-side hermetic space U. The test of thesealing performance of the back-side sealing projection 49 is performedby checking whether the pressurized gas in the back-side hermetic spaceU leaks through the back-side sealing projection 49.

An embodiment of a leak checking method performed by using the leakchecking apparatus 60 shown in FIG. 16 will now be described withreference to the flow chart of FIG. 17. First, the substrate W isinterposed between the first holding member 38 and the second holdingmember 40 with the back surface and the front surface of the substrate Wexposed through the opening 38 b of the first holding member 38 and theopening 40 a of the second holding member 40, respectively, whereby thesubstrate W is held by the substrate holder 24 (step 1). When holdingthe substrate W with the substrate holder 24, the front-side sealingprojection 117 of the second holding member 40 seals the gap between aperipheral portion of the front surface of the substrate W and thesecond holding member 40, the back-side sealing projection 49 of thefirst holding member 38 seals the gap between a peripheral portion ofthe back surface of the substrate W and the first holding member 38, andthe intermediate sealing member 116 seals the gap between the firstholding member 38 and the second holding member 40, thereby forming theinternal space R in the substrate holder 24 by the first holding member38, the second holding member 40 and the substrate W.

Next, the front-side sealing cap 119 is disposed on the second holdingmember 40 of the substrate holder 24 such that the front-side sealingcap 119 covers the front surface of the substrate W, exposed through theopening 40 a, and the second holding member 40. The back-side sealingcap 120 is disposed on the first holding member 38 of the substrateholder 24 such that the back-side sealing cap 120 covers the backsurface of the substrate W, exposed through the opening 38 b, and thefirst holding member 38 (step 2). The front-side sealing cap 119 and theback-side sealing cap 120 may be disposed on the substrate holder 24either simultaneously or at different timings.

The front-side gas seal 121 of the front-side sealing cap 119 is pressedagainst the second holding member 40 by the pressing mechanism 62 toseal the gap between the second holding member 40 and the front-sidesealing cap 119 with the front-side gas seal 121, thereby forming thefront-side hermetic space S between the front-side sealing cap 119 andthe substrate holder 24. The back-side gas seal 122 of the back-sidesealing cap 120 is pressed against the first holding member 38 by thepressing mechanism 130 to seal the gap between the first holding member38 and the back-side sealing cap 120 with the back-side gas seal 122,thereby forming the back-side hermetic space U between the back-sidesealing cap 120 and the substrate holder 24 (step 3).

The operation controller 95 selects a pressure command value from thepressure range stored therein, and sends the pressure command value tothe pressure regulator 93 (step 4). The operation controller 95 opensthe holder-side valve 101, the master-side valve 102, the front-sidebranch valve 126 and the back-side branch valve 129 while keeping thefirst vent valve 103 and the second vent valve 104 closed. Thepressurized gas flows through the front-side branch line 125, theback-side branch line 128 and the differential-pressure check line 75into the front-side hermetic space S, the back-side hermetic space U andthe master container 80 (step 5). The pressures of the pressurized gasin the front-side hermetic space S, the back-side hermetic space U andthe master container 80 are regulated by the pressure regulator 93, andthe operation of the pressure regulator 93 is controlled by theoperation controller 95. More specifically, the pressure regulator 93operates to maintain the pressurized gas in the pressurized-gasintroduction line 70 at a pressure corresponding to the pressure commandvalue.

When a predetermined amount of time has elapsed since the holder-sidevalve 101, the master-side valve 102, the front-side branch valve 126and the back-side branch valve 129 were opened, the operation controller95 closes the holder-side valve 101 and the master-side valve 102. Thefront-side hermetic space S, the back-side hermetic space U and themaster container 80 are sealed by the holder-side valve 101 and themaster-side valve 102. The front-side hermetic space S, the back-sidehermetic space U and the master container 80 are each filled with thepressurized gas having the same pressure (step 6).

With the holder-side valve 101 and the master-side valve 102 closed, thedifferential-pressure measuring device 85 measures a pressure differencebetween the pressurized gas in the master container 80 and thepressurized gas in the two hermetic spaces S, U (step 7). Thedifferential-pressure measuring device 85 determines whether thepressure difference has exceeded a threshold value within the set time(step 8). If the pressure difference has not exceeded the thresholdvalue within the set time, the differential-pressure measuring device 85emits a signal indicating that there is no leakage of the pressurizedgas in the front-side hermetic space S and the pressurized gas in theback-side hermetic space U (i.e. the front-side sealing projection 117and the back-side sealing projection 49 are functioning properly) (step9). If the pressure difference has exceeded the threshold value withinthe set time, the differential-pressure measuring device 85 emits asignal indicating that there is leakage of the pressurized gas in thefront-side hermetic space S and/or the pressurized gas in the back-sidehermetic space U (i.e. there is a failure of the front-side sealingprojection 117 and/or the back-side sealing projection 49) (step 10).

The operation controller 95 opens the first vent valve 103 and thesecond vent valve 104 to discharge the pressurized gas in the front-sidehermetic space S and the back-side hermetic space U and the pressurizedgas in the master container 80 through the holder-side exhaust line 97and the master-side exhaust line 98. The leak check is performed in thismanner to test the sealing performances of the front-side sealingprojection 117 and the back-side sealing projection 49.

FIG. 18 is a flow chart illustrating an embodiment of a leak checkingmethod performed by using the leak checking apparatus 60 shown in FIG.16. Steps 1 to 6 are the same as the steps 1 to 6 shown in FIG. 17, anda duplicated description thereof is omitted. After step 6, the operationcontroller 95 closes the back-side branch valve 129 to shut offcommunication between the differential-pressure measuring device 85 andthe back-side hermetic space U (step 7). The differential-pressuremeasuring device 85 measures a pressure difference between thepressurized gas in the master container 80 and the pressurized gas inthe front-side hermetic space S (step 8). The differential-pressuremeasuring device 85 determines whether the pressure difference hasexceeded a threshold value within the set time (step 9). If the pressuredifference has not exceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is no leakage of the pressurized gas in the front-side hermeticspace S (i.e. the front-side sealing projection 117 is functioningproperly) (step 10). If the pressure difference has exceeded thethreshold value within the set time, the differential-pressure measuringdevice 85 emits a signal indicating that there is leakage of thepressurized gas in the front-side hermetic space S (i.e. there is afailure of the front-side sealing projection 117) (step 11).

Next, the operation controller 95 opens the back-side branch valve 129and closes the front-side branch valve 126 to allow communicationbetween the differential-pressure measuring device 85 and the back-sidehermetic space U and to shut off communication between thedifferential-pressure measuring device 85 and the front-side hermeticspace S (step 12 of FIG. 19). The differential-pressure measuring device85 measures a pressure difference between the pressurized gas in themaster container 80 and the pressurized gas in the back-side hermeticspace U (step 13). The differential-pressure measuring device 85determines whether the pressure difference has exceeded a thresholdvalue within the set time (step 14). If the pressure difference has notexceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is no leakage of the pressurized gas in the back-side hermeticspace U (i.e. the back-side sealing projection 49 is functioningproperly) (step 15). If the pressure difference has exceeded thethreshold value within the set time, the differential-pressure measuringdevice 85 emits a signal indicating that there is leakage of thepressurized gas in the back-side hermetic space U (i.e. there is afailure of the back-side sealing projection 49) (step 16).

The operation controller 95 opens the front-side branch valve 126, thefirst vent valve 103 and the second vent valve 104 to discharge thepressurized gas in the front-side hermetic space S and the back-sidehermetic space U and the pressurized gas in the master container 80through the holder-side exhaust line 97 and the master-side exhaust line98. The leak check is performed in this manner to test the sealingperformances of the front-side sealing projection 117 and the back-sidesealing projection 49.

FIG. 20 is a flow chart illustrating an embodiment of a leak checkingmethod performed by using the leak checking apparatus 60 shown in FIG.16. Steps 1 to 4 are the same as the steps 1 to 4 shown in FIG. 17, anda duplicated description thereof is omitted. The operation controller 95opens the holder-side valve 101, the master-side valve 102 and thefront-side branch valve 126 while keeping the first vent valve 103, thesecond vent valve 104 and the back-side branch valve 129 closed. Thepressurized gas flows through the front-side branch line 125 and thedifferential-pressure check line 75 into the front-side hermetic space Sand the master container 80 (step 5). The pressures of the pressurizedgas in the front-side hermetic space S and the master container 80 areregulated by the pressure regulator 93, and the operation of thepressure regulator 93 is controlled by the operation controller 95. Morespecifically, the pressure regulator 93 operates to maintain thepressurized gas in the pressurized-gas introduction line 70 at apressure corresponding to the pressure command value.

When a predetermined amount of time has elapsed since the holder-sidevalve 101, the master-side valve 102 and the front-side branch valve 126were opened, the operation controller 95 closes the holder-side valve101 and the master-side valve 102. The front-side hermetic space S andthe master container 80 are sealed by the holder-side valve 101 and themaster-side valve 102. The front-side hermetic space S and the mastercontainer 80 are each filled with the pressurized gas having the samepressure (step 6).

While the holder-side valve 101 and the master-side valve 102 areclosed, the differential-pressure measuring device 85 measures apressure difference between the pressurized gas in the master container80 and the pressurized gas in the front-side hermetic space S (step 7).The differential-pressure measuring device 85 determines whether thepressure difference has exceeded a threshold value within the set time(step 8). If the pressure difference has not exceeded the thresholdvalue within the set time, the differential-pressure measuring device 85emits a signal indicating that there is no leakage of the pressurizedgas in the front-side hermetic space S (i.e. the front-side sealingprojection 117 is functioning properly) (step 9). If the pressuredifference has exceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas in the front-side hermetic spaceS (i.e. there is a failure of the front-side sealing projection 117)(step 10). The operation controller 95 opens the first vent valve 103,the second vent valve 104 and the front-side branch valve 126 todischarge the pressurized gas in the front-side hermetic space S and thepressurized gas in the master container 80 through the holder-sideexhaust line 97 and the master-side exhaust line 98 (step 11).

Next, the operation controller 95 closes the first vent valve 103, thesecond vent valve 104 and the front-side branch valve 126, andsubsequently opens the holder-side valve 101, the master-side valve 102and the back-side branch valve 129. The pressurized gas flows throughthe back-side branch line 128 and the differential-pressure check line75 into the back-side hermetic space U and the master container 80 (step12 of FIG. 21). The pressures of the pressurized gas in the back-sidehermetic space U and the master container 80 are regulated by thepressure regulator 93, and the operation of the pressure regulator 93 iscontrolled by the operation controller 95. More specifically, thepressure regulator 93 operates to maintain the pressurized gas in thepressurized-gas introduction line 70 at a pressure corresponding to thepressure command value.

When a predetermined amount of time has elapsed since the holder-sidevalve 101, the master-side valve 102 and the back-side branch valve 129were opened, the operation controller 95 closes the holder-side valve101 and the master-side valve 102. The back-side hermetic space U andthe master container 80 are sealed by the holder-side valve 101 and themaster-side valve 102. The back-side hermetic space U and the mastercontainer 80 are each filled with the pressurized gas having the samepressure (step 13).

With the holder-side valve 101 and the master-side valve 102 closed, thedifferential-pressure measuring device 85 measures a pressure differencebetween the pressurized gas in the master container 80 and thepressurized gas in the back-side hermetic space U (step 14). Thedifferential-pressure measuring device 85 determines whether thepressure difference has exceeded a threshold value within the set time(step 15). If the pressure difference has not exceeded the thresholdvalue within the set time, the differential-pressure measuring device 85emits a signal indicating that there is no leakage of the pressurizedgas in the back-side hermetic space U (i.e. the back-side sealingprojection 49 is functioning properly) (step 16). If the pressuredifference has exceeded the threshold value within the set time, thedifferential-pressure measuring device 85 emits a signal indicating thatthere is leakage of the pressurized gas in the back-side hermetic spaceU (i.e. there is a failure of the back-side sealing projection 49) (step17).

The operation controller 95 opens the first vent valve 103, the secondvent valve 104 and the back-side branch valve 129 to discharge thepressurized gas in the back-side hermetic space U and the pressurizedgas in the master container 80 through the holder-side exhaust line 97and the master-side exhaust line 98. The leak check is performed in thismanner to test the sealing performances of the front-side sealingprojection 117 and the back-side sealing projection 49. In theabove-described embodiment, the sealing performance of the front-sidesealing projection 117 in contact with the front surface of thesubstrate W is tested first, and then the sealing performance of theback-side sealing projection 49 in contact with the back surface of thesubstrate W is tested. In an embodiment, the sealing performance of theback-side sealing projection 49 may be tested first, followed by thetest of the sealing performance of the front-side sealing projection117.

An embodiment of an electroplating apparatus, including the plating tank10, the substrate holder 24 and the leak checking apparatus 60 describedabove, will now be described. FIG. 22 shows an overall layout plan viewof the electroplating apparatus. As shown in FIG. 22, the electroplatingapparatus includes two cassette tables 212 each for receiving thereon acassette 210 in which substrates, such wafers, are housed, an aligner214 for aligning an orientation flat or a notch of a substrate in apredetermined direction, and a spin-rinse drier 216 for drying a platedsubstrate by rotating it at a high speed. The electroplating apparatusfurther includes a substrate attachment and detachment section 220 forsetting a substrate on a substrate holder 24 and taking the substrateout of the substrate holder 24. In the electroplating apparatus isdisposed a substrate transport device 222, comprised of a transportrobot, for transporting a substrate between the cassette table 212, thealigner 214, the spin-rinse drier 216 and the substrate attachment anddetachment section 220. The electroplating apparatus is provided withthe operation controller 95 (not shown in FIG. 22) which is capable ofcontrolling not only the leak checking apparatus 60 but the entireelectroplating apparatus.

The electroplating apparatus further includes a stocker 224 for storingand temporarily placing substrate holders 24 therein, a pre-wetting tank226 for immersing a substrate in pure water, a pre-soaking tank 228 foretching away a surface oxide film, e.g. on a surface seed layer of thesubstrate, a first water-cleaning tank 230 a for cleaning the substrateafter pre-soaking, a blow tank 232 for draining the cleaned substratedry, a second water-cleaning tank 230 b for cleaning the platedsubstrate, and a plurality of plating tanks 10, all of which arearranged in this order. The plating tanks 10 are surrounded by anoverflow tank 12. A paddle drive device 246 for driving the paddle 32(see FIG. 1) is disposed adjacent to the overflow tank 12.

Further, the electroplating apparatus includes a substrate-holdertransport device 240 for transporting a substrate holder 24 togetherwith a substrate. The substrate-holder transport device 240 has a firsttransporter 242 for transporting a substrate between the substrateattachment and detachment section 220 and the stocker 224, and a secondtransporter 244 for transporting the substrate between the stocker 224,the pre-wetting tank 226, the pre-soaking tank 228, the water-cleaningtanks 230 a, 230 b, the blow tank 232 and the plating tank 10. Thesubstrate-holder transport device 240 may be provided with only thefirst transporter 242 without being provided with the second transporter244.

The substrate attachment and detachment section 220 includes a flatstage plate 252 which is laterally slidable along rails 250. Twosubstrate holders 24 are placed in a horizontal position and in parallelon the stage plate 252. After transferring a substrate between onesubstrate holder 24 and the substrate transport device 222, the stageplate 252 is slid laterally, and a substrate is then transferred betweenthe other substrate holder 24 and the substrate transport device 222.

A sequence of plating performed by the thus-constructed platingapparatus will now be described. First, one substrate is taken by thesubstrate transport device 222 out of the cassette 210 mounted on thecassette table 212, and the substrate is placed on the aligner 214,which aligns an orientation flat or a notch of the substrate in apredetermined direction. After the alignment, the substrate istransported to the substrate attachment and detachment section 220 bythe substrate transport device 222.

Two substrate holders 24, housed in the stocker 224, are simultaneouslygripped by the first transporter 242 of the substrate-holder transportdevice 240, and transported to the substrate attachment and detachmentsection 220. The substrate holders 24 are lowered in a horizontalposition to simultaneously place the two substrate holders 24 on thestage plate 252 of the substrate attachment and detachment section 220.

The substrate is transported by the substrate transport device 222 toone substrate holder 24 on the stage plate 252, and is placed, with itsto-be-plated surface facing upward, on the substrate support surface 38a (see FIG. 2) of the first holding member 38 of the substrate holder24. The substrate is set on the substrate holder 24 by the substrateattachment and detachment section 220. More specifically, the substrateattachment and detachment section 220 operates the coupling mechanism 41(see FIG. 2) to secure the second holding member 40 of the substrateholder 24 to the first holding member 38. The substrate, with theto-be-plated surface exposed through the opening 40 a (see FIG. 2) ofthe substrate holder 24, is held by the substrate holder 24. Aftercompletion of the loading of the substrate to the one substrate holder24, the stage plate 252 is slid laterally, and another substrate is seton the other substrate holder 24 in the same manner. Thereafter, thestage plate 252 is returned to its original position.

Though not shown diagrammatically, instead of the substrate attachmentand detachment section 220 on which two substrate holders 24 are to beplaced in a horizontal position, it is possible to provide a fixingstation which supports two substrate holders 24, which have beentransported by the first transporter 242, in a vertical position (or atan angle slightly inclined from the vertical). The substrate holders 24can be brought into a horizontal position by rotating the fixingstation, holding the substrate holders 24 in a vertical position,through 90 degrees.

The above-described leak checking apparatus 60 is incorporated in thesubstrate attachment and detachment section 220. The leak check isperformed on a substrate holder 24 holding a substrate. A substrate,held by a substrate holder 24 which has passed the leak check, issubjected to plating. A substrate holder 24 which has failed to pass theleak check is opened, and a substrate is removed from the substrateholder 24 and is returned to the cassette 210 on the cassette table 212.The substrate holder 24 that has failed to pass the leak check isgripped by the first transporter 242 of the substrate-holder transportdevice 240, and returned to the stocker 224, where the substrate holder24 remains unused. The substrate holder 24 is taken out of the stocker224 e.g. after completion of the operation, and subjected to anappropriate treatment.

A plating process for a substrate, held by a substrate holder 24 whichhas passed the leak check, will now be described. The substrate holder24 holding the substrate is transported by the substrate-holdertransport device 240 to the pre-wetting tank 226, and is lowered toimmerse the substrate, together with the substrate holder 24, in apre-wetting liquid in the pre-wetting tank 226.

Next, the substrate holder 24 holding the substrate is transported bythe substrate-holder transport device 240 to the pre-soaking tank 228.In the pre-soaking tank 228, a surface oxide film of the substrate isetched away, thereby exposing a clean metal surface. Thereafter, thesubstrate holder 24 holding the substrate is transported by thesubstrate-holder transport device 240 to the first water-cleaning tank230 a, and the surface of the substrate is cleaned with pure water inthe first water-cleaning tank 230 a.

The substrate holder 24 holding the cleaned substrate is gripped by thesecond transporter 244 of the substrate-holder transport device 240 andtransported to the plating tank 10, and immersed in a plating solutionin the plating tank 10. Plating of the surface of the substrate isperformed by applying a voltage between the anode 26 (see FIG. 1) andthe substrate while reciprocating the paddle 32 (see FIG. 1) parallel tothe surface of the substrate by means of the paddle drive device 246.

After completion of the plating, the application of the voltage and thereciprocation of the paddle 32 are stopped. The substrate holder 24holding the plated substrate is gripped by the second transporter 244 ofthe substrate-holder transport device 240 and transported to the secondwater-cleaning tank 230 b, and the surface of the substrate is cleanedwith pure water in the second water-cleaning tank 230 b.

Next, the substrate holder 24 holding the cleaned substrate istransported by the second transporter 244 of the substrate-holdertransport device 240 to the blow tank 232, where water droplets,adhering to the substrate holder 24 and the surface of the substrate,are removed to dryness by blowing of air or N₂ gas. Thereafter, thefirst transporter 242 of the substrate-holder transport device 240 gripsthe dried substrate holder 24 and places it on the stage plate 252 ofthe substrate attachment and detachment section 220.

The substrate attachment and detachment section 220 releases thecoupling mechanism 41 of one of the two substrate holders 24 to detachthe second holding member 40 from the first holding member 38. Theplated substrate is then taken out of the substrate holder 24 by thesubstrate transport device 222, and transported to the spin rinse drier216. The spin rinse drier 216 first cleans the substrate with purewater, and then spin-dries the substrate by rotating it at a high speed.The spin-dried substrate is returned by the substrate transport device222 to the cassette 210.

After or in parallel with returning the substrate, which has been takenout of the one substrate holder 24, to the cassette 210, the stage plate252 is slid laterally and the substrate is taken out of the othersubstrate holder 24. The substrate is then spin-dried and returned tothe cassette 210 in the same manner.

While the substrate W used in the above-described embodiments is acircular substrate such as a wafer, the present invention can be appliedalso to a quadrangular substrate. The components of a substrate holderfor holding a quadrangular substrate each have a shape that is adaptedto the shape of the substrate. For example, the above-described opening38 b may be a quadrangular opening which is smaller than the overallsize of the quadrangular substrate. Various sealing elements, such asthe second sealing projection 47 and the first sealing projection 48,may each have a shape that is adapted to the shape of the quadrangularsubstrate. The shapes of other components may also be appropriatelymodified without departing from the technical concept described herein.

The previous description of embodiments is provided to enable a personskilled in the art to make and use the present invention. Moreover,various modifications to these embodiments will be readily apparent tothose skilled in the art, and the generic principles and specificexamples defined herein may be applied to other embodiments. Therefore,the present invention is not intended to be limited to the embodimentsdescribed herein but is to be accorded the widest scope as defined bylimitation of the claims.

What is claimed is:
 1. A leak checking method comprising: holding asubstrate with a substrate holder, the substrate holder including afirst holding member and a second holding member, the second holdingmember having an opening through which a surface of the substrate isexposed; pressing a sealing projection of the second holding memberagainst the surface of the substrate when holding the substrate with thesubstrate holder; covering the surface of the substrate, exposed throughthe opening, and the sealing projection with a sealing cap; forming ahermetic space between the sealing cap and the substrate holder;introducing a pressurized gas into the hermetic space; and detecting adecrease in pressure of the pressurized gas in the hermetic space. 2.The leak checking method according to claim 1, further comprising:selecting a pressure command value from a preset pressure range; sendingthe selected pressure command value to a pressure regulator; andregulating the pressure of the pressurized gas in the hermetic spacewith the pressure regulator based on the pressure command value.
 3. Theleak checking method according to claim 2, wherein the pressure rangeincludes a pressure of a plating solution which is expected to beapplied to the sealing projection when the substrate, held by thesubstrate holder, is immersed in the plating solution.
 4. The leakchecking method according to claim 3, wherein a lower limit of thepressure range is a value of a pressure of the plating solution which isexpected to be applied to an uppermost portion of the sealing projectionwhen the substrate, held by the substrate holder in a vertical position,is immersed in the plating solution.
 5. The leak checking methodaccording to claim 3, wherein an upper limit of the pressure range is avalue obtained by multiplying a factor by a value of a pressure of theplating solution which is expected to be applied to a lowermost portionof the sealing projection when the substrate, held by the substrateholder in a vertical position, is immersed in the plating solution. 6.The leak checking method according to claim 1, wherein forming thehermetic space between the sealing cap and the substrate holdercomprises pressing the sealing cap against the substrate holder to forma hermetic space between the sealing cap and the substrate holder. 7.The leak checking method according to claim 1, further comprising:pressing a partition seal of the sealing cap against the substrateholder to divide the hermetic space into a first hermetic space and asecond hermetic space, wherein introducing the pressurized gas into thehermetic space comprises supplying the pressurized gas into either thefirst hermetic space or the second hermetic space, wherein the sealingprojection comprises a first sealing projection, and the second holdingmember further includes a second sealing projection which contacts thefirst holding member, and wherein the first sealing projection and thesecond sealing projection face the first hermetic space and the secondhermetic space, respectively.
 8. A leak checking method comprising:holding a substrate with a substrate holder, the substrate holderincluding a first holding member and a second holding member, the firstholding member having a first opening and a back-side sealingprojection, the second holding member having a second opening and afront-side sealing projection; pressing the front-side sealingprojection and the back-side sealing projection against a front surfaceand a back surface, respectively, of the substrate when holding thesubstrate with the substrate holder; covering the front surface of thesubstrate, exposed through the second opening, and the front-sidesealing projection with a front-side sealing cap; forming a front-sidehermetic space between the front-side sealing cap and the substrateholder; covering the back surface of the substrate, exposed through thefirst opening, and the back-side sealing projection with a back-sidesealing cap; forming a back-side hermetic space between the back-sidesealing cap and the substrate holder; introducing a pressurized gas intothe front-side hermetic space and/or the back-side hermetic space; anddetecting a decrease in pressure of the pressurized gas in thefront-side hermetic space and/or the back-side hermetic space.
 9. Theleak checking method according to claim 8, further comprising: selectinga pressure command value from a preset pressure range; sending theselected pressure command value to a pressure regulator; and regulatingthe pressure of the pressurized gas in the front-side hermetic spaceand/or the back-side hermetic space with the pressure regulator based onthe pressure command value.
 10. The leak checking method according toclaim 9, wherein the pressure range includes a pressure of a platingsolution which is expected to be applied to the front-side sealingprojection and the back-side sealing projection when the substrate, heldby the substrate holder, is immersed in the plating solution.
 11. Theleak checking method according to claim 10, wherein a lower limit of thepressure range is a value of a pressure of the plating solution which isexpected to be applied to an uppermost portion of the front-side sealingprojection or an uppermost portion of the back-side sealing projectionwhen the substrate, held by the substrate holder in a vertical position,is immersed in the plating solution.
 12. The leak checking methodaccording to claim 10, wherein an upper limit of the pressure range is avalue obtained by multiplying a factor by a value of a pressure of theplating solution which is expected to be applied to a lowermost portionof the front-side sealing projection or a lowermost portion of theback-side sealing projection when the substrate, held by the substrateholder in a vertical position, is immersed in the plating solution. 13.An electroplating method comprising: setting a substrate, to be plated,on a substrate holder in a substrate attachment and detachment section;performing the leak checking method according to claim 1; immersing thesubstrate, held by the substrate holder, in a plating solution; andplating the substrate.
 14. The electroplating method according to claim13, wherein the leak checking method is performed in the substrateattachment and detachment section.
 15. A leak checking apparatus forchecking for leakage of a fluid through a sealing projection of asubstrate holder when the sealing projection is being pressed against asurface of a substrate held by the substrate holder which includes afirst holding member and a second holding member, the second holdingmember having the sealing projection and an opening through which asurface of the substrate is to be exposed, said apparatus comprising: asealing cap having a shape that covers the opening and the sealingprojection; a pressurized-gas supply system configured to introduce apressurized gas into a hermetic space formed between the sealing cap andthe substrate holder; and a pressure decrease detector configured todetect a decrease in pressure of the pressurized gas in the hermeticspace.
 16. The leak checking apparatus according to claim 15, furthercomprising: a pressure regulator configured to regulate the pressure ofthe pressurized gas based on a pressure command value; and an operationcontroller that stores a preset pressure range therein, wherein theoperation controller is configured to send the pressure command value,which has been selected from the pressure range, to the pressureregulator.
 17. An electroplating apparatus comprising: a substrateattachment and detachment section configured to set a substrate, to beplated, on a substrate holder; a plating tank configured to hold aplating solution therein; and the leak checking apparatus according toclaim
 15. 18. The electroplating apparatus according to claim 17,wherein the leak checking apparatus is incorporated in the substrateattachment and detachment section.
 19. A leak checking apparatus forchecking for leakage of a fluid through a front-side sealing projectionand a back-side sealing projection of a substrate holder when thefront-side sealing projection and the back-side sealing projection arebeing pressed against a front surface and a back surface, respectively,of a substrate held by the substrate holder which includes a firstholding member and a second holding member, the first holding memberhaving a first opening and the back-side sealing projection, the secondholding member having a second opening and the front-side sealingprojection, said apparatus comprising: a front-side sealing cap having ashape that covers the second opening and the front-side sealingprojection; a back-side sealing cap having a shape that covers the firstopening and the back-side sealing projection; a pressurized-gas supplysystem configured to introduce a pressurized gas into a front-sidehermetic space formed between the front-side sealing cap and thesubstrate holder, and into a back-side hermetic space formed between theback-side sealing cap and the substrate holder; and a pressure decreasedetector configured to detect a decrease in pressure of the pressurizedgas in the front-side hermetic space and the back-side hermetic space.20. The leak checking apparatus according to claim 19, furthercomprising: a pressure regulator configured to regulate the pressure ofthe pressurized gas based on a pressure command value; and an operationcontroller that stores a preset pressure range, wherein the operationcontroller is configured to send the pressure command value, which hasbeen selected from the pressure range, to the pressure regulator.
 21. Anelectroplating apparatus comprising: a substrate attachment anddetachment section configured to set a substrate, to be plated, on asubstrate holder; a plating tank configured to hold a plating solutiontherein; and the leak checking apparatus according to claim
 19. 22. Theelectroplating apparatus according to claim 21, wherein the leakchecking apparatus is incorporated in the substrate attachment anddetachment section.